Cotahuasi
Valley. Although we were now in the zone of light annual rains, it
was evident from the extraordinary irrigation system that agriculture
here depends very largely on ability to bring water down from the
great mountains in the interior. Most of the terraces and irrigation
canals were built centuries ago, long before the discovery of America.

No part of the ancient civilization of Peru has been more admired
than the development of agriculture. Mr. Cook says that there is no
part of the world in which more pains have been taken to raise crops
where nature made it hard for them to be planted. In other countries,
to be sure, we find reclamation projects, where irrigation canals serve
to bring water long distances to be used on arid but fruitful soil. We
also find great fertilizer factories turning out, according to proper
chemical formula, the needed constituents to furnish impoverished soils
with the necessary materials for plant growth. We find man overcoming
many obstacles in the way of transportation, in order to reach great
regions where nature has provided fertile fields and made it easy to
raise life-giving crops. Nowhere outside of Peru, either in historic or
prehistoric times, does one find farmers spending incredible amounts
of labor in actually creating arable fields, besides bringing the
water to irrigate them and the guano to fertilize them; yet that
is what was done by the ancient highlanders of Peru. As they spread
over a country in which the arable flat land was usually at so great
an elevation as to be suitable for only the hardiest of root crops,
like the white potato and the oca, they were driven to use narrow
valley bottoms and steep, though fertile, slopes in order to raise the
precious maize and many of the other temperate and tropical plants
which they domesticated for food and medicinal purposes. They were
constantly confronted by an extraordinary scarcity of soil. In the
valley bottoms torrential rivers, meandering from side to side, were
engaged in an endless endeavor to tear away the arable land and bear
it off to the sea. The slopes of the valleys were frequently so very
steep as to discourage the most ardent modern agriculturalist. The
farmer might wake up any morning to find that a heavy rain during
the night had washed away a large part of his carefully planted
fields. Consequently there was developed, through the centuries,
a series of stone-faced andenes, terraces or platforms.